Effect of heat treatment on the bending behavior of tri-layered Cu/Al/Cu composite plates

Bending and fracture behaviors of tri-layered Cu/Al/Cu composite plates were processed by roll-bonding and the effects of work hardening and displacement rate sensitivity during bending on the overall bending behavior and fracture were investigated. As-roll-bonded composite exhibited the extensive load plateau before a relatively rapid load drop. The more localized bending in the as-roll-bonded Cu/Al/Cu clad composite can be attributed to the near-zero work hardening rate in bending. For the Cu/Al/Cu composites annealed at 300 °C and up to 450 °C, the pronounced work hardening during bending tends to distribute the bending deformation uniformly. For the as-roll-bonded Cu/Al/Cu composite, a fatal crack perpendicular to the Cu/Al interface through the bottom Cu layer was formed by the large tensile stress associated with the severely localized bending. A large crack parallel to the interface adjacent to the fatal crack through the bottom Cu layer appeared to have propagated in Al layer, not along the interface between Al and the bottom Cu layer, suggesting the excellent bonding between Al and Cu in the as-roll-bonded Cu/Al/Cu. For annealed clad composites at 500 °C, the localized bending is thought to be caused by the growth of cracks along the interface reaction layer, resulting in the fracture of bottom Cu layer.